Drill bit with application specific side cutting efficiencies

ABSTRACT

A drill bit includes a drill bit body and first and second blades formed on the drill bit body. The first blade has first cutting elements defining a first profile length and an adjacent first gauge section having a first gauge length. The second blade has second cutting elements defining a second profile length and an adjacent second gauge section having a second gauge length which is shorter than the first gauge length of the first blade. Certain ones of the second cutting elements on the second blade rotationally overlap with a portion of the first gauge section on the first blade.

CROSS-REFERENCE AND PRIORITY CLAIM

This application claims the benefit of U.S. Provisional Application for Patent Ser. No. 60/746,778 filed May 8, 2006, the disclosure of which is hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to rotary drill bits for rotary drilling of subterranean formations.

BACKGROUND OF THE INVENTION

Subsurface formation drilling to recover hydrocarbons is well known in the art. The equipment for such subsurface formation drilling typically comprises a drill string having a rotary drill bit attached thereto that is lowered into a borehole. A rotary table or similar device rotates the drill string, resulting in a corresponding rotation of the drill bit. The rotation advances the drill bit downwardly, causing it to cut through the subsurface formation (e.g., by abrasion, fracturing, and/or shearing action). Drilling fluid is pumped down a channel in the drill string and out the drill bit to cool the bit and flush away debris that may have accumulated. The drilling fluid travels back up the borehole through an annulus formed between the drill string and the borehole.

Many types of drill bits have been developed, including roller cone bits, fixed cutter bits (or “drag bits”), and the like. For each type of drill bit, several patterns of cutting elements (or “cutters”) are possible, including spiral patterns, straight radial patterns, and the like. Different types of cutting elements have also been developed, including milled cutting elements, tungsten carbide inserts (“TCI”), polycrystalline-diamond compacts (“PDC”), and natural diamond cutting elements. The selection of which drill bit, cutting element type, and cutting element pattern to use for a given subsurface formation can depend on a number of factors. For example, certain combinations of drill bit, cutting element type, and cutting element pattern drill more efficiently and effectively in hard formations than others. Another factor is the range of hardness encountered when drilling through the different formation layers.

One common pattern for drill bit cutting elements is to arrange them in a spiral configuration, an example of which is shown in FIGS. 1A and 1B. As can be seen, a spiral pattern drill bit 100 is composed of several sections, including a bit body 102, a shank 104, and a threaded connector 106 for connecting the drill bit 100 to a drill string. Flats 108 on the shank 104 allow a tool, such as wrench, to grip the drill bit 100, making it possible (or at least easier) to screw the drill bit 100 onto the drill string. Blades 110 a, 110 b, 110 c, 110 d, 110 e, and 110 f are formed on the drill bit 100 for holding a plurality of cutting elements 112. The cutting elements 112 include superabrasive faces that usually have identical geometries (i.e., size, shape, and orientation), although different positions and/or cutting angles on the blades 110 a-f may be used. Also visible are drill fluid outlets 114 that conduct the drilling fluid out of the drill bit 100, carrying away any debris and cuttings that may have accumulated.

In the spiral configuration and other radial configuration drill bits, the cutting elements 112 are placed at selected radial positions with respect to a central longitudinal axis A. In addition, the positions of the cutting elements 112 on one blade 110 a-f are staggered relative to the positions of the cutting elements 112 on another blade 110 a-f. The result is that a cutting surface of one cutting element 112 overlaps the cutting surface of at least one other cutting element 112 in their cutting profiles, which is the area outlined by the cutting surfaces when the cutting elements are rotated onto the same radial plane. Thus, each cutting element 112 removes a lesser volume of material than would be the case if it were positioned so that no overlapping occurred.

The collection of cutting elements 112 on each blade 110 a-f define a profile length L which originates at or near central longitudinal axis A and terminates at the point P where the gauge section 120 of the blade begins. The gauge section 120 on each blade 110 a-f has a length M (which starts at point P and ends at point Q). It will be noted that, in the drill bit shown in FIG. 1A, the length M of the gauge section 120 is identical on each blade 110 a-f. In some drill bit configurations, such as the one illustrated in FIG. 1A, the lengths L of the profile for the cutting elements 112 need not be the same for all included blades 110 a-f.

FIG. 2A illustrates schematically in a simplified form two blades 110 of a drill bit like that shown in FIGS. 1A and 1B and the corresponding positional and length M relationships of the gauge section 120. FIG. 2A further shown a scenario where the two blades 110 have corresponding profile lengths L. Conversely, FIG. 2B illustrates schematically in a simplified form two blades 110 of a drill bit like that shown in FIGS. 1A and 1B which do not have corresponding profile length L (i.e., one length L2 is shorter than another length L1), but do have corresponding positional and length M relationships with respect to the gauge sections 120.

SUMMARY OF THE INVENTION

In accordance with an embodiment, a drill bit comprises: a drill bit body and first and second blades formed on said drill bit body. Said first blade has a first plurality of cutting elements defining a first profile length and an adjacent first gauge section having a first gauge length. Said second blade has a second plurality of cutting elements defining a second profile length and an adjacent second gauge section having a second gauge length which is shorter than the first gauge length of the first blade.

In accordance with another embodiment, a drill bit comprises: a drill bit body; and a plurality of blades formed on said drill bit body, each blade having a length and including along the length a section for cutting elements and, adjacent to the section for cutting elements, a gauge section. The plurality of blades include: a first blade having a first gauge section with a first length along the length of the first blade; and a second blade having a second gauge section with a second length along the length of the second blade which is shorter than the first length of the first gauge section.

In accordance with another embodiment, a drill bit comprises: a drill bit body; a first blade formed on said drill bit body, and a second blade formed on said drill bit body. The first blade includes a first region extending along a length of the first blade supporting a first plurality of cutting elements, and a first gauge section extending further along the length of the first blade adjacent to the first region. The second blade includes a second region extending along a length of the second blade supporting a second plurality of cutting elements which rotationally overlap with the first plurality of cutting elements, an extension region extending further along the length of the second blade adjacent to the second region and supporting a third plurality of cutting elements which rotationally overlap with a first portion of the first gauge section of the first blade, and a second gauge section extending further along the length of the second blade adjacent to the extension region which rotationally overlaps with a second portion of the first gauge section of the first blade.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional aspects of the invention will be apparent to those of ordinary skill in the art in view of the detailed description of various embodiments, which is made with reference to the drawings, wherein:

FIGS. 1A and 1B, described previously, illustrate a perspective view and a bottom view of a prior art fixed cutter drill bit;

FIGS. 2A and 2B, described previously, illustrate schematically in a simplified form two blades of a prior art drill bit like that shown in FIGS. 1A and 1B;

FIGS. 3A and 3B illustrate schematically in a simplified form two blades of a drill bit having application specific side cutting efficiencies; and

FIG. 4 illustrates a perspective view of the drill bit shown in FIGS. 3A and 3B.

DETAILED DESCRIPTION OF THE DRAWINGS

It should be noted that the drawings are provided for illustrative purposes only and are not intended to be a blueprint or manufacturing drawings, nor are they drawn to any particular scale. Like or similar parts in the drawings have the same reference number.

FIG. 3A illustrates schematically in a simplified form two blades 110 of a drill bit 200 having application specific side cutting efficiencies. Each blade 110 of the drill bit 200 includes a plurality of cutting elements 112 that are placed at selected radial positions with respect to a central longitudinal axis A. Although not specifically illustrated in FIG. 3A, the positions of the cutting elements 112 on one blade 110 are preferably radially staggered relative to the positions of the cutting elements 112 on another blade 110. The collection of cutting elements 112 on each blade 110 define a profile length L which originates at or near central longitudinal axis A and terminates at the point P where the gauge section 120 of the blade begins. The gauge section 120 on each blade 110, which is adjacent to the section including the cutting elements 112 along the length of the blade, has a length M (which starts at point P and ends at point Q). It will be noted that, in the drill bit 200 shown in FIG. 3A, the length M1 of the gauge section 120 on one of the blades 110(1) is longer than the length M2 of the gauge section 120 on the other of the blades 110(2). This is caused by the inclusion of additional cutting elements 112 in an extension region 202 which corresponds to the gauge section on other blade 110(2). It will further be noted that the gauge section 120 having the gauge length M1 on blade 110(1) starts at a first distance away from a center axis A of the drill bit 200, and the gauge section 120 having the gauge length M2 starts at a second distance, which is different than the first distance, away from a center axis of the drill bit (see, points P). Again, this is caused by the inclusion of additional cutting elements 112 in the extension region 202 which pushes point P on blade 110(2) further away from the axis A. In a preferred implementation as shown in the figures, the gauge section 120 having the gauge length M1 on blade 110(1) terminates at a third distance away from the center axis A of the drill bit 200, and the gauge section 120 having the gauge length M2 on blade 110(2) terminates at a fourth distance, which is the same as the third distance, away from the center axis of the drill bit (see, points Q).

With reference to FIG. 3B, the two blades 110 of the drill bit 200 do not have a profile length L which starts at the central longitudinal axis A. It will further be noted that even in this scenario the length M1 of the gauge section 120 on one of the blades 110(1) is longer than the length M2 of the gauge section 120 on the other of the blades 110(2). Again, this is caused by the inclusion of additional cutting elements 112 in an extension region 202 which corresponds to the gauge section on other blade.

Thus, the drill bit 200 includes in the extension region 202 additional cutting elements 112 along the length of the blade 110(2) which overlap into an area which is occupied on another blade 110(1) by a non-cutter (smooth) surface 204 of the gauge section 120 (as opposed to being occupied by cutting elements 112 positioned along the length of the blade such as is the case in the curved regions 206 of the blades). In the application specific side cutting concept illustrated by FIGS. 3A and 3B, at least one included blade 110(2) has cutting elements 112 positioned in a region 202 of the blade corresponding to the gauge section 120 of another blade 110(1), and thus this blade 110(2) has a shorter in length M2 gauge section than the length M1 for the gauge section of the other blade 110(1). Thus, if the blades 110(1) and 110(2) where rotated into a common plane so as to be overlapping, the cutting elements 112 in the extension region 202 of blade 110(2) would overlap a portion of the gauge section 120 of blade 110(1). In other words, the cutting elements in the extension region 202 of blade 110(2) rotationally overlap with a portion of the gauge section 120 of blade 110(1).

Reference is now made to FIG. 4 which illustrates a perspective view of the drill bit 200 utilizing the blade configurations shown in FIGS. 3A and 3B. Blade 110 d of drill bit 200 is shown to have a gauge section 120 of length M1 (see, right hand side of FIGS. 3A and 3B and blade 110(1)), while blades 110 b and 110 c are shown to have gauge sections 120 of length M2 (see, left hand side of FIGS. 3A and 3B and blade 110(2)). Blades 110 b and 110 d include a set of cutting elements 112 in the region 206 which do not have a profile length L which starts at the central longitudinal axis A (compare to left hand side of FIG. 3B). Conversely, the cutting elements 112 of blade 110 c form a blade having a profile length L which starts at or near the central longitudinal axis A (compare to the right hand side of FIG. 3B and either blade of FIG. 3A).

In the particular example illustrated by FIG. 4, the extension regions 202 on blades 110 b and 110 c are formed by the addition of two cutting elements 112 to the profile length L at a position on the blade which rotationally corresponds to non-cutter (smooth) surface 204 of the gauge section 120 on another blade (for example, blade 110 d). It will, of course, be understood that the addition of two cutting elements is just exemplary (FIGS. 3A and 3B show the addition of three cutting elements), and that the added number of cutting elements 112 is selectable by the bit designer in order to achieve desired application specific side cutting efficiencies. Preferably, two or more additional cutting elements 112 are included within the extension region 202 of a given blade 110.

FIG. 4 further shows that blades 110 b and 110 c both use a length M2 for their gauge sections 120. In this context, it will be noted that the shorter length M2 gauge section 120 provided on two different blades 110 of the bit 200 need not be identical. In some situations it may be advantageous for the blades 110 of the bit 200 to include gauge section 120 lengths M2 on two included blades which are different from each other (but nonetheless still shorter than the length M1). The various included lengths M2 on the blades 110 of the bit 200 are selectable by the bit designer in order to achieve desired application specific side cutting efficiencies.

Thus, a drill bit 200 as described herein has different profile lengths L and extents for one or more blades 110. That is, one or more blades 110 may have cutting elements 112 mounted further along the side (i.e., the area normally occupied by the gauge section 120 and further away from the axis of the bit) than other blades 110, resulting in a longer (i.e., further extending) profile L and shorter gauge length M2 for those one or more blades. This can be seen in the exemplary drill bit profile shown in FIG. 3A, where the profile length for at least one of the blades (on the left hand side) is longer and extends further than the profile length for at least one other blade (on the right hand side).

In general, a further extending profile length L (with a shorter gauge length M2) is more effective for maneuverability of the drill bit 200, whereas a shorter profile length (with a longer gauge length M1) is more effective for holding the drilling angle. Similarly, for maneuverability in hard formation materials, further extending profile lengths (with a shorter gauge length M2) may be needed. In soft formation materials, however, there may be an advantage to the use of a shorter profile length (with a longer gauge length M1). Stability of the drill bit may also be affected by the profile lengths and extents.

Depending on the particular formation material, a drill bit 200 having some blades 110 with longer and/or further extending profile lengths (and a shorter gauge length M2) and other blades 110 with shorter profile lengths (and a longer gauge length M1) may be used (in a mixed and matched selection by the bit designer) to optimize stability and maneuverability. For example, certain formation materials may need half of the blades to have a longer and/or further extending profile length (and a shorter gauge length M2), while other formation materials may only need one of the blades to have a longer and/or further extending profile length (and a shorter gauge length M2), and so on. Likewise, different profile lengths and extents (and different gauge lengths M) may be mixed together, for example, longer and/or further extending profile lengths (with short gauge lengths) may be combined with intermediately extending profile lengths (having intermediate gauge lengths) and/or shorter profile lengths (with long gauge lengths).

While the present invention has been described with reference to one or more particular embodiments, those skilled in the art will recognize that many changes may be made thereto without departing from the scope of the invention. Accordingly, each of the foregoing embodiments and obvious variations thereof is contemplated as falling within the scope of the claimed invention, as is set forth in the following claims. 

1. A drill bit, comprising: a drill bit body; first and second blades formed on said drill bit body; wherein said first blade has a first plurality of cutting elements defining a first profile length and an adjacent first gauge section having a first gauge length; and wherein said second blade has a second plurality of cutting elements defining a second profile length and an adjacent second gauge section having a second gauge length which is shorter than the first gauge length of the first blade.
 2. The drill bit of claim 1, wherein, when the first and second blades are rotated into a common plane, the second plurality of cutting elements include at least one cutting element positioned on the second blade so as to overlap a portion of the first gauge section on the first blade.
 3. The drill bit of claim 1, wherein, when the first and second blades are rotated into a common plane, the second plurality of cutting elements include at least two cutting elements positioned on the second blade so as to overlap a portion of the first gauge section on the first blade.
 4. The drill bit of claim 1, wherein the first and second profile lengths for the first and second pluralities of cutting elements start at different distances away from a center axis of the drill bit.
 5. The drill bit of claim 1, wherein the first gauge section having the first gauge length starts at a first distance away from a center axis of the drill bit, and wherein the second gauge section having the second gauge length starts at a second distance, different than the first distance, away from the center axis of the drill bit.
 6. The drill bit of claim 5, wherein the first gauge section having the first gauge length terminates at a third distance away from the center axis of the drill bit, and wherein the second gauge section having the second gauge length terminates at a fourth distance, which is the same as the third distance, away from the center axis of the drill bit.
 7. A drill bit, comprising: a drill bit body; a plurality of blades formed on said drill bit body, each blade having a length and including along the length a section for cutting elements and, adjacent to the section for cutting elements, a gauge section; wherein the plurality of blades include: a first blade having a first gauge section with a first length along the length of the first blade; and a second blade having a second gauge section with a second length along the length of the second blade which is shorter than the first length of the first gauge section.
 8. The drill bit of claim 7, wherein the first length of the first gauge section starts at a first distance away from a center axis of the drill bit, and wherein the second length of the second gauge section starts at a second distance, different than the first distance, away from the center axis of the drill bit.
 9. The drill bit of claim 8, wherein the first length of the first gauge section terminates at a third distance away from the center axis of the drill bit, and wherein the second length of the second gauge section terminates at a fourth distance, which is the same as the third distance, away from the center axis of the drill bit.
 10. A drill bit, comprising: a drill bit body; a first blade formed on said drill bit body, the first blade including a first region extending along a length of the first blade supporting a first plurality of cutting elements, and a first gauge section extending further along the length of the first blade adjacent to the first region; and a second blade formed on said drill bit body, the second blade including a second region extending along a length of the second blade supporting a second plurality of cutting elements which rotationally overlap with the first plurality of cutting elements, an extension region extending further along the length of the second blade adjacent to the second region and supporting a third plurality of cutting elements which rotationally overlap with a first portion of the first gauge section of the first blade, and a second gauge section extending further along the length of the second blade adjacent to the extension region which rotationally overlaps with a second portion of the first gauge section of the first blade.
 11. The drill bit of claim 10, wherein the first and second pluralities of cutting elements are identical in number.
 12. The drill bit of claim 10, wherein the first gauge section has a first gauge length and the second gauge section has a second gauge length which is shorter than the first gauge length.
 13. The drill bit of claim 12, wherein the first gauge length terminates at a first distance away from a center axis of the drill bit, and wherein the second gauge length terminates at a second distance, which is the same as the first distance, away from the center axis of the drill bit.
 14. The drill bit of claim 10 wherein the first region on the first blade and the second region on the second blade start at different distances away from a center axis of the drill bit. 